In the UV irradiation of surfaces, in particular for sterilization purposes, it can be advantageous if at least during the irradiation, where appropriate also before and/or after, a purging of the spatial area between radiation emitter and surface takes place using a purging gas. This is intended to remove UV-radiation-absorbing gases between the surface and the UV radiation emitter, at least during the irradiation. Nitrogen or noble gases in particular are suitable as a purging gas. In other irradiation processes, too, a defined atmosphere between radiation emitter and surface, and consequently the use of a suitable process gas, may be advantageous. The term process gas is used in the following as a generic term for one or more suitable gases for purging or for other processes before, during and/or after the irradiation.
In order to irradiate readily accessible surfaces, for example flat films, the prior art approach has been to supply the purging gas by means of a separate device arranged around the radiation emitter or from the side. A disadvantageous aspect is the requirement for additional equipment and the necessary coordination between purging arrangement and radiation emitter. Furthermore, said systems generally cannot be used inside hollow spaces with narrow access openings such as canisters or bottles for space reasons.
A UV radiation emitter based on a one-sided dielectric barrier discharge is known from the publication EP 1 506 567 B1. For this purpose the discharge vessel 2 is filled with xenon. So-called excimers are formed during the gas discharge, which preferably is driven by means of a pulsed operating method described in U.S. Pat. No. 5,604,410. Excimers are excited molecules, e.g. Xe2*, which emit electromagnetic radiation when returning to the usually unbound ground state. In the case of Xe2*, the maximum of the molecule band radiation lies in the region of approx. 172 nm. In order to generate the dielectric barrier discharge, a first helix-shaped electrode 23 is arranged coaxially inside the tubular discharge vessel 2. Six strip-shaped outer electrodes 8a-8f are arranged in parallel with one another and mutually spaced apart on the outside of the discharge vessel 2.
A tubular UV radiation emitter based on a two-sided dielectric barrier discharge is disclosed in the publication EP 0 607 960 A1. The radiation emitter vessel is formed in the manner of a coaxial double tube arrangement in which an inner tube and an outer tube are joined to one another to form a gas-tight seal at the two front ends. In this arrangement the discharge chamber enclosed by the discharge vessel extends between inner and outer tube.
A flat discharge lamp based on a two-sided dielectric barrier discharge is disclosed in the publication EP 1 232 518 B1. The dielectric barrier discharge is generated between a base plate and a top plate, the circumferential sealing frame and cone-shaped supporting elements being molded into the top plate. The electrodes are applied as two interlocking comb-like line structures onto the outside of the base plate.